JPS6235539A - Manufacture of semiconductor device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] When filling contact holes formed in an insulating layer on an electron-conducting semiconductor region with aluminum, a thin tungsten film is formed at the junction with a silicon substrate to prevent contact resistance defects. Treatment methods to prevent.

[Industrial application field]

The present invention relates to a contact hole filling method that prevents the occurrence of contact resistance defects.

In the manufacture of integrated semiconductor devices such as ICs and LSIs, semiconductor regions with different conductivity types are created on a semiconductor substrate by methods such as thermal diffusion of impurity ions or ion implantation, and these regions are used to form semiconductor devices. There is.

Here, the method for manufacturing an integrated circuit is to form an insulating layer on a semiconductor substrate (substrate hereinafter) including semiconductor regions of different conductivity types, form a wiring pattern on this insulating layer, and Various semiconductor devices are manufactured by forming contact holes by drilling holes until they reach the semiconductor region, and connecting circuits to wiring patterns through the contact holes.

Here, substrate materials include single semiconductors represented by silicon (St) and compound semiconductors such as gallium arsenide (GaAs) and indium phosphide (InP), but Si is the most commonly used, with a diameter of 5. High-purity single crystals of inch or 6 inches are grown, and this is made to a thickness of approximately 500 mm.
A substrate that is sliced into IJm and subjected to surface treatments such as polishing and cleaning is used as a substrate.

In addition, gold (AuL) is used as a material for forming wiring patterns.
Although aluminum (Al) and the like are used, AI is often used due to its cost.

The present invention relates to a manufacturing method for preventing poor contact in contact holes in an integrated circuit using Si as a substrate and A1 as a wiring material.

[Conventional technology]

FIG. 3 is a cross-sectional view illustrating a conventional contact hole filling method, in which a high concentration electron conduction type (hereinafter n + ) semiconductor region 2 is formed in a substrate 1. A contact hole 4 is formed by selectively etching the 8i layer 3 formed above until it reaches the semiconductor 5M region 2;
After filling this hole using the selective growth method of AI, the insulating layer 3
Vacuum deposition method on top.

A1 layer 5 is formed by sputtering or the like, and then photolithography (photolithography or electron beam lithography) is applied to this layer.
Fine wiring patterns are created using

Here, the conventional contact hole forming method and hole filling method will be explained in the case where the insulating layer 3 is as thick as about 1 μm.

After surface treatment, the substrate 1 is exposed to oxygen containing a small amount of water vapor (
02) Create a silicon dioxide (SiOz) layer of approximately 6000 layers by heat treatment at a temperature of approximately 1000°C in an air stream, then place the substrate 1 in a chemical vapor deposition apparatus (CVD apparatus) and deposit monosilane (SiHa). 0□ or nitrous oxide (
An insulating layer 3 made of SiO2 and having a thickness of approximately 1 μm is formed on the substrate 1 by supplying gas with N zo ) to cause a CVD reaction.

The reason why the insulating layer 3 is formed in two steps is that it is inefficient to grow the insulating layer 3 by 1 μm only by heat treatment.

Next, the substrate 1 is placed in a reactive ion etching (RIE) device, and carbon tetrafluoride (CF4) is used as a reactive gas.
), the contact hole 4 is formed by selectively dry etching the contact hole forming position of the insulating layer 3, which is made by opening the resist, until it reaches the substrate 1.

Next, the substrate 1 is transferred to a CVD apparatus, and while it is heated to about 200°C, trimethylaluminum (At(CH)3) is
] Or triisobutylaluminum (AI (Ca I
By supplying Is) 3) as a reactive gas, A1 is selectively grown only on the semiconductor region 2 at the bottom of the contact hole 4 to fill the hole, and after filling the hole, the insulating layer of the substrate 1 is grown. A1 using sputtering method etc. on top of 3.
1i5, a cross-sectional structure as shown in FIG. 3 is created.

However, at the bottom of the contact hole 4 filled in this way, since the AI is in contact with the n+ semiconductor region, the AI atoms and Si atoms are mutually diffused, forming the p+ semiconductor region 6 shown by the broken line. is likely to occur, and in this case pn
Because of the bonding, the bonded portion is in a state of high resistance and is likely to end up in a state of poor contact.

Therefore, the yield in the process of filling the contact hole 4 was poor, and an improvement was needed.

[Problem that the invention seeks to solve]

As mentioned above, when filling a contact hole formed on the n+ semi-semiconductor territory with AI, it is necessary to use AI and S.
Mutual diffusion of the i atoms tends to form a p metacarpal conductor region, which causes poor contact.

Therefore, the problem is how to eliminate this phenomenon.

[Effect]

The present invention forms a thin electrically conductive dam layer made of tungsten (W) at the boundary where the contact hole 4 contacts the n++ conductor region 2, thereby blocking interdiffusion between AI atoms and Si atoms. It eliminates defects.

In this case, the resistivity of W is 5.48 x 10-6 Ωcm
Although it is high compared to 2.62 x 10-'ΩclI+ of A1, it can be ignored compared to the resistivity of the semiconductor region.

〔Example〕

FIG. 1 is a cross-sectional view of a contact hole portion filled by applying the present invention, and FIGS. 2(A) to (C) are cross-sectional views of the hole filling process.

That is, FIG. 2(A) shows a state in which a contact hole 4 reaching the n+ semiconductor region 2 is formed by drilling a hole in the insulating layer 3. A thin film 7 of W is formed on the bottom of the contact hole 4 in contact with it.

The method is to
After setting it in a CVD device and thoroughly evacuation, supplying tungsten hexafluoride (WFs) using H2 as a carrier,
The substrate 1 is heated to approximately 300°C while maintaining the vacuum level at 1 torr.
When heated, W selectively grows only on the semiconductor region 2 at the bottom of the contact hole 4 due to the reaction of 2WF6+3Si→3SiF4+2W.

In this example, 300
We were able to create a W film for ~400 people.

FIG. 2(B) shows the W thin film 7 formed in this manner.

Next, the substrate 1 is transferred to a CVD apparatus, and while it is heated to about 200°C, trimethylaluminum (Al(CH3)3
] Or triisobutylaluminum (Al(C4H9
) 3) as a reaction gas, argon (Ar) as a carrier gas, and hydrogen (H2) as a decomposition promoting gas, AI(CH3) +H2→A1+CH4 or AI(Ca Hs) +H2→Al+CI
(Due to the reaction in step 4, AI is at W3 at the bottom of contact hole 4.
A18 is selectively grown only on the film 7 to fill the hole.

The reason for this is that in the reducing atmosphere of hydrogen, W is reduced and the metal surface is exposed, so that growth is more likely to occur than on the insulating layer 3 made of Sto2.

In this way, only the contact hole 4 is filled with At as shown in FIG. 2(C).

Next, by forming Aljii 5 on the insulating layer 3 by sputtering or the like, a cross-sectional structure as shown in FIG. 1 is created.

When the contact hole 4 is filled in this way, conduction becomes complete, and the defect rate in the conventional hole filling process was about 20%, but by implementing the present invention, it was possible to reduce it to 2 to 3%. .

〔Effect of the invention〕

As described above, by implementing the present invention in which a thin film of W is formed at the contact portion of a contact hole to prevent interdiffusion between AI atoms and Si atoms, the yield in the contact hole filling process can be greatly improved. becomes possible.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a contact hole portion in which the present invention is implemented, Fig. 2 (A) to (C) are cross-sectional views of the contact hole filling process according to the present invention, and Fig. 3 is a cross-sectional view of a conventional contact hole portion. It is a sectional view. In the figure, 1 is a substrate, 2.6 is a semiconductor region, 3 is an insulating layer, 4 is a contact hole, 5 is an A1 layer,
7 is a W thin film, and 8 is an At. It is. Figure\g

Claims (1)

[Claims] A silicon substrate (1) having an electron-conducting semiconductor region (2)
) is selectively etched to form a contact hole (4) in the insulating layer (3) formed on the contact hole (4).
) to grow aluminum to fill the holes.
A method for manufacturing a semiconductor device, characterized in that aluminum is grown after a tungsten thin film (7) is previously formed on the semiconductor region (2) of the contact hole (4).